#ifndef SECURE_LAYER 
#define SECURE_LAYER SECURE_LAYER
#endif
typedef struct user
{
    char* user_name;
    char* user_key;
}User;
int check_user(User u);
int check_visible(User u , char* topic_key);
int add_user(User u );
int set_user(User u);
int del_user(User u);